Impact of biogenic volatile organic compounds on peroxyacetyl nitrate production in the southeast United States
Our atmosphere is arguably the fundamental entity that has made life on Earth possible. Knowledge of the delicate nature of our atmosphere continues to spread as "green" initiatives promote awareness of human influence on the environment. However, many climate scientists fear that unless immediate mitigation occurs, the reversal of human impact on our planet will be impossible, leading to unknown consequence. Perturbations to natural processes are likely to cause drastic change to the planet as we know it and ultimately result in significant health issues. It is important to push the boundaries of our understanding of atmospheric processes with intent to reduce the impact human activity has already imposed. This work focuses on the production of peroxyacetyl nitrate (PAN), a compound known for its adverse effects on plant life and human health, in two parts; (1) using relative production ratios to calculate relative PAN production using a chemical tracer, and (2) application of an explicit chemical model in simulating relative production of PAN in a southeastern US forest environment. Chapter two examines our current understanding of the isoprene photo-oxidation mechanism particularly in regards to the formation of two peroxyacyl nitrates: PAN and MPAN. A relationship when production is greater than loss processes between MPAN and PAN was found to be relatively constant throughout the experiment with a ratio of MPAN/PAN of 1.5 ± 19% RSD. This relationship can be used in ambient conditions to approximate isoprene contribution to PAN production, since MPAN is formed solely through isoprene oxidation. Absolute concentrations of isoprene nitrates and APNs are found to be significantly oversimulated. This shows an incomplete understanding of the isoprene oxidation mechanism and begs for continued studies to further our understanding of this chemical system. Chapter three applied the observed ratio of MPAN/PAN within the chamber experiment to an ambient calculation to approximate isoprene contribution to PAN production in the SOAS campaign. Results show that an average of 44% ± 16% of PAN production results from the oxidation of isoprene. Further analysis using a 0-D ambient model show isoprene contributes 50-70% to PAN production, which statistically is not different from calculations using MPAN/PAN ratio from chamber experimentation. Chapter four reflects on the results of this study to provide insight to the future of the field. Suggestions for future studies to improve understanding of the PAN mechanism are presented, as well as suggestions for future ambient modeling with a transport model.
Shepson, Purdue University.
Atmospheric Chemistry|Chemistry|Environmental science
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